1. Field of the Invention
The present invention relates to an antenna substrate for a non-contact communication apparatus provided with two coils insulated and isolated from each other.
2. Description of Related Art
In a short-range wireless communication of inductor coupling type, non-contact communication is performed by bringing two antenna coils close to each other so as to establish a magnetic coupling between these two antenna coils. However, when a metal substance is arranged on the back side of either one of these antenna coils, the metal substance becomes closer to the other antenna coil as these two antenna coils are brought closer to each other. Consequently, the effective antenna inductance of the other antenna coil is gradually lowered due to the eddy current generated on the surface of the metal substance. Irrespective of whether these two antenna coils are located close to each other, communication characteristics may be considerably deteriorated, or the non-contact communication apparatuses may be unable to communicate.
Accordingly, measures of providing a thick magnetic sheet between a metal substance and the back side of the antenna coil to reduce the eddy current generated in the metal substance, has been generally taken (see, for example, Japanese Unexamined Patent Application Publication No. 2006-285709).